Posted: Jul 31, 2017 4:34 pm
Part of the problem in the world of taxonomy, lies with the very nature of Linnaean taxonomy. Linnaean taxonomy was based upon the principle that shared anatomical features are an indication of relatedness, but when alighting upon this principle, Linnaeus did not take the next step, and ask why this should be so. His remit was classification, and he contented himself with taking advantage of comparative anatomy as an informative classification tool. If he ever did ask why anatomy constituted a pointer to relatedness, then I suspect he did not pursue the matter further, because he could not find a ready answer to the question. He thus contented himself with treating this as a brute fact.
But the mere fact that he did accept this brute fact, placed him in a position, had he pursued the question vigorously, to have alighted upon evolutionary ideas 112 years before Darwin. Because Linnaeus was, through his classification work, the first major scientific figure to accept the idea of relatedness of species.
That reliance upon comparative anatomy was, however, a two edged sword. As we now know, shared anatomy is frequently an indicator of shared ancestry. But when one delves into the fine detail, the picture sometimes becomes more complicated. Sometimes, members of widely separated lineages can exhibit, at least superficially, anatomical similarities, and it takes detailed analysis to reveal the homoplasious nature thereof.
We had to wait for Darwin to pursue the question vigorously, and ask why shared anatomy is an indication of relatedness. His answer was beautifully simple - shared anatomy is indicative of inheritance from a common ancestor. In effect, evolutionary theory unified the biosphere by extending genealogy to species.
But that extension, and the subsequent development of the ability to track that genealogy genetically, has shone a spotlight on the manner in which many of our everyday terms do not capture the fine detail of the underlying reality. The word 'monkey' is a prime example, because it is applied in everyday usage to an assemblage of organisms that is not monophyletic. The New World Monkeys, taken in isolation, are a monophyletic clade, but the moment you include the Old World Monkeys, which themselves comprise, in isolation, another monopphyletic clade, the resulting assemblage is paraphyletic. That compound assemblage does not include all of the descendants of the common ancestor of the assemblage. The two clades in question share an immediate common ancestor (and the the assemblage is not polyphyletic), but the assemblage does not include the Hominoidea, which are also descendants of that ancestor.
Of course, another part of the problem lies in the fact that without the vast body of prior work performed by Linnaeus and his successor taxonomists, Darwin would not have had the data with which to inject rigour into any formulation of evolutionary theory. Without detailed anatomical breakdowns of tens of thousands of organisms, a proper analysis of the relevant trends could not have been performed. We had to wait for the anatomical data, before it became possible to construct cladistic data, and even then, formal cladistics did not appear until long after Darwin's seminal work. Even though Darwin brought descent into the centre of biology, the modern tools to map descent were, of course, not available to him, even though he almost certainly understood the importance of performing such mapping.
Plus, even modern, cladistically aware taxonomists, have to start somewhere, and the Linnaean paradigm has, for a long time, been the only tried and tested game in town. But, cladistically aware taxonomists know from the start, that a Linnaean taxonomic designation, along with its associated type material, is merely a static snapshot of the state of a species at the time of description. By its very nature, a Linnaean taxonomic designation cannot include dynamic information about the changing genetic state of the species population over time. Which leads to the interesting conundrum I covered on several occasions in the past, whereby it could be possible for distant future members of a designated Linnaean species to be unable to reproduce with the current set of ancestral individuals. At which point, a new Linnaean designation would be needed, and the old designation would correspond to a technically extinct taxon. For more on this, see my various discussions of the wonderful world of Cynotilapia afra, which now provides a case in point.
As for the "are we monkeys?" question, the correct answer is that we and monkeys reside in sister clades.
But the mere fact that he did accept this brute fact, placed him in a position, had he pursued the question vigorously, to have alighted upon evolutionary ideas 112 years before Darwin. Because Linnaeus was, through his classification work, the first major scientific figure to accept the idea of relatedness of species.
That reliance upon comparative anatomy was, however, a two edged sword. As we now know, shared anatomy is frequently an indicator of shared ancestry. But when one delves into the fine detail, the picture sometimes becomes more complicated. Sometimes, members of widely separated lineages can exhibit, at least superficially, anatomical similarities, and it takes detailed analysis to reveal the homoplasious nature thereof.
We had to wait for Darwin to pursue the question vigorously, and ask why shared anatomy is an indication of relatedness. His answer was beautifully simple - shared anatomy is indicative of inheritance from a common ancestor. In effect, evolutionary theory unified the biosphere by extending genealogy to species.
But that extension, and the subsequent development of the ability to track that genealogy genetically, has shone a spotlight on the manner in which many of our everyday terms do not capture the fine detail of the underlying reality. The word 'monkey' is a prime example, because it is applied in everyday usage to an assemblage of organisms that is not monophyletic. The New World Monkeys, taken in isolation, are a monophyletic clade, but the moment you include the Old World Monkeys, which themselves comprise, in isolation, another monopphyletic clade, the resulting assemblage is paraphyletic. That compound assemblage does not include all of the descendants of the common ancestor of the assemblage. The two clades in question share an immediate common ancestor (and the the assemblage is not polyphyletic), but the assemblage does not include the Hominoidea, which are also descendants of that ancestor.
Of course, another part of the problem lies in the fact that without the vast body of prior work performed by Linnaeus and his successor taxonomists, Darwin would not have had the data with which to inject rigour into any formulation of evolutionary theory. Without detailed anatomical breakdowns of tens of thousands of organisms, a proper analysis of the relevant trends could not have been performed. We had to wait for the anatomical data, before it became possible to construct cladistic data, and even then, formal cladistics did not appear until long after Darwin's seminal work. Even though Darwin brought descent into the centre of biology, the modern tools to map descent were, of course, not available to him, even though he almost certainly understood the importance of performing such mapping.
Plus, even modern, cladistically aware taxonomists, have to start somewhere, and the Linnaean paradigm has, for a long time, been the only tried and tested game in town. But, cladistically aware taxonomists know from the start, that a Linnaean taxonomic designation, along with its associated type material, is merely a static snapshot of the state of a species at the time of description. By its very nature, a Linnaean taxonomic designation cannot include dynamic information about the changing genetic state of the species population over time. Which leads to the interesting conundrum I covered on several occasions in the past, whereby it could be possible for distant future members of a designated Linnaean species to be unable to reproduce with the current set of ancestral individuals. At which point, a new Linnaean designation would be needed, and the old designation would correspond to a technically extinct taxon. For more on this, see my various discussions of the wonderful world of Cynotilapia afra, which now provides a case in point.
As for the "are we monkeys?" question, the correct answer is that we and monkeys reside in sister clades.